1. Field of Invention
The present invention relates to a source driver. More particularly, the present invention relates to a source driver for image scrolling.
2. Description of Related Art
A liquid crystal display device includes a source driver to store and transfer bits of pixel values of an image from a core processor such as a central processing unit (CPU) onto a word line on the panel. Conventional source drivers transfer bits of pixel values through a frame memory for storing the bits and a line buffer for buffering the bits with corresponding address index onto the data bus. The address index positions the pixels on their respective locations on the display. When the displayed images are scrolled vertically on the display panel, the bits of pixel values of the images loads from the frame memory to the line buffer with address indexes assigned in sequence. Therefore, when the bits of pixel values of an image is scrolled vertically, the address index of the bits will sequentially be assigned address indexes by an address index circuit in the line buffer, so that the bits are sequentially re-located in a vertical direction according the sequence of the address indexes.
However, since the sequence of address indexes corresponds to vertical image scrolling on the display, horizontal image scrolling may not be able to use the same sequence of address indexes to re-locate the bits of pixel values horizontally. Horizontal scrolling is necessary in applications such as screen savers and image presentations, where images often move in various directions on the display. In order for images to be scrolled horizontally, the CPU will have to generate new bits of pixel values of the images and refresh the frame memory with the new bits of pixel values, so that without an indexing algorithm, the bits of pixel values of an image will need to be constantly re-generated for the image to be scrolled horizontally. The conventional source driver and method consumes extra power and also is an inefficient method for the usage of CPU recourses.
For the forgoing reasons, there is a need for a new source driver having a new method of refreshing the frame memory for image scrolling so that the bits of pixel values of the image does not need to be re-generated.